It is not clear that locking everything down will solve the issue of the virus in the long term. What if it turns out that it actually makes things worse?
Long term it's entirely possibly that the virus will simply re-emerge once everything opens am up again.
The UK plan as I understand it is to slowly increase the measures we take to eek out the number of cases over a longer period of time allowing the NHS to cope. They absolutely do not want a peak next Winter as that really would be difficult for the NHS to deal with.